[evolution-data-server] I#355 - Camel: Ignore empty output from "Pipe to program" filter

[Milan Crha <mcrha src gnome org>]

commit 9daed72ba210c6fc7d0c301ddf1fd5a390189183
Author: Milan Crha <mcrha redhat com>
Date:   Fri Sep 17 11:09:02 2021 +0200

    I#355 - Camel: Ignore empty output from "Pipe to program" filter
    
    Closes https://gitlab.gnome.org/GNOME/evolution-data-server/-/issues/355

 src/camel/camel-filter-driver.c | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/src/camel/camel-filter-driver.c b/src/camel/camel-filter-driver.c
index 9df9eee9d..7553daa78 100644
--- a/src/camel/camel-filter-driver.c
+++ b/src/camel/camel-filter-driver.c
@@ -1083,6 +1083,7 @@ pipe_to_system (struct _CamelSExp *f,
        CamelStream *stream, *mem;
        GPid child_pid;
        GError *error = NULL;
+       GByteArray *bytes;
        GPtrArray *args;
        child_watch_data_t child_watch_data;
        GSource *source;
@@ -1157,6 +1158,11 @@ pipe_to_system (struct _CamelSExp *f,
 
        g_object_unref (stream);
 
+       bytes = camel_stream_mem_get_byte_array (CAMEL_STREAM_MEM (mem));
+
+       if (!bytes || !bytes->len)
+               goto wait;
+
        g_seekable_seek (G_SEEKABLE (mem), 0, G_SEEK_SET, NULL, NULL);
 
        parser = camel_mime_parser_new ();